[ONOS-4563][ONOS-4564][ONOS-4551][ONOS-4538]defect fix

Change-Id: Ia3fe844e1e846d2e1d2c4359eefc815e7767aef9
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangEnum.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangEnum.java
index a9f80e3..df702e9 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangEnum.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangEnum.java
@@ -50,7 +50,7 @@
 /**
  * Represents the ENUM data type information.
  */
-public class YangEnum implements YangCommonInfo, Parsable {
+public class YangEnum implements YangCommonInfo, Parsable, Comparable<YangEnum> {
 
     /**
      * Named value for the ENUM.
@@ -226,4 +226,12 @@
     public void validateDataOnExit() throws DataModelException {
         // TODO auto-generated method stub, to be implemented by parser
     }
+
+    @Override
+    public int compareTo(YangEnum otherEnum) {
+        if (this.namedValue.equals(otherEnum.getNamedValue())) {
+            return 0;
+        }
+        return new Integer(this.value).compareTo(otherEnum.getValue());
+    }
 }